The present invention relates to a system for recharging the battery of a motor vehicle.
More specifically, the invention relates to a system including:
a current generator including an alternator with an armature winding and a field winding, and a rectifier, the output of the generator being connected to a terminal of the battery,
a switch connected to the said terminal of the battery,
an indicator lamp connected in series with the switch, and
a voltage regulator which has first and second inputs connected to the output of the generator and to the lamp respectively, and which is activated through the switch and the lamp, the regulator including:
a circuit for regulating the current supplied to the field winding of the alternator in dependence on the voltage, supplied by the generator,
a driver circuit for the lamp, adapted to turn on the lamp when the switch is closed and the generator is not operating and to turn off the lamp when the switch is open, and when the generator is operating whilst while the switch is closed,
a supply circuit for supplying the voltage regulator circuit, and
control circuitry connected to the lamp for enabling the supply circuit to operate when a current is flowing in the lamp and when the generator is operating.
A battery-charging system for a motor vehicle of the type specified is described, for example, in British patent application No. 2,164,508.
In this known recharging system, when the key-operated switch is closed, the voltage regulator is supplied through the indicator lamp. When the alternator is subsequently set in operation (as a result of the starting of the internal combustion engine of the vehicle), the flow of current through the lamp is interrupted and the lamp goes out. The voltage regulator is nevertheless supplied through a control circuit connected to one winding or phase of the alternator. When the alternator is rotated, an asymmetrical alternating signal is applied to the input of the control circuit. The control circuit includes an R-C mean-value detector. As soon as the mean value of the signal taken from one phase of the alternator exceeds a predetermined minimum threshold, the control circuit enables the supply circuit to supply the voltage regulator.
In the prior-art system described above, if there is a leakage of current through one or more diodes of the rectifier bridge of the generator, a direct current may reach the control circuit and, in particular, the capacitor of the mean-value detector of that circuit. This direct current can simulate the phase signal when the alternator is not operating and may result in the undesired activation of the supply circuit even when the key-operated switch is open. Inappropriate activation of the voltage-regulator supply circuit results in the detrimental consumption of energy from the battery.